1. Field of the Invention
The present invention relates to an inching control device and in particular to an inching control device provided in a work vehicle equipped with an inching function, the device used for controlling clutch oil pressure supplied to a hydraulic clutch during an inching operation. The present invention further relates to a work vehicle equipped with the above inching control device.
2. Background Information
A work vehicle is equipped with an inching function that causes slipping in a hydraulic clutch provided in a transmission to reduce the vehicle speed. By using the inching function, the vehicle speed can be reduced while maintaining the engine rotation speed at a predetermined rotation speed. For example, a motor grader may travel while performing grading work with a blade. In this case, the operator is able to adjust the vehicle speed while suppressing a reduction in the driving power of the blade by activating an inching pedal to produce slipping in the clutch.
When the inching operation time increases in a work vehicle equipped with the inching function, the heat value of the clutch increases and wear of the clutch increases. The clutch may become damaged if the inching operation is continued while being overloaded.
Techniques for protecting the clutch during the inching operation have been proposed as disclosed in Japanese Laid-open Patent Publication No. 2009-186003, Japanese Laid-Open Patent Publication No. H06-344782, and Japanese Laid-open Patent Publication No. 2003-166634.
A load on the clutch is calculated during inching and a control is performed so that the engine rotation speed is lowered when the load on the clutch exceeds a threshold value in the work vehicle described in Japanese Laid-open Patent Publication No. 2009-186003. The heat value of the clutch is detected during inching and an alarm is issued when the heat value exceeds a reference value in a device described in Japanese Laid-Open Patent Publication No. H06-344782. The temperature of a clutch plate is detected during inching and the clutch is fastened or released when the detection temperature exceeds a threshold value in the device described in Japanese Laid-open Patent Publication No. 2003-166634.